Hello Michal:
I think this thread is related to OVN. In any case, I've analyzed your logs from the Neutron point of view. Those are basically the key points in your logs: [1]. The Neutron server receives the request to create and bind a new port. Both the DHCP agent and the OVS agent provision the port (8a472e87-4a7a-4ad4-9fbb-fd9785136611).
Neutron server sends the "network-vif-plugged" event at 08:51:05.635 and receives the ACK from Nova at 08:51:05.704. Nova server creates the corresponding event for the instance on the compute0:
2021-11-25 08:51:05.692 23 INFO nova.api.openstack.compute.server_external_events [req-393fcb9a-5c68-4b0a-af1b-661e73d947cb 01a75e3a9a9148218916d3beafae2120 7d16babef0524b7dade9a59b0a3569e1 - default default] Creating event network-vif-plugged:8a472e87-4a7a-4ad4-9fbb-fd9785136611 for instance 09eff2ce-356f-430f-ab30-5de58f58d698 on compute0
Nova compute agent receives this server event:
2021-11-25 08:51:05.705 8 DEBUG nova.compute.manager [req-393fcb9a-5c68-4b0a-af1b-661e73d947cb 01a75e3a9a9148218916d3beafae2120 7d16babef0524b7dade9a59b0a3569e1 - default default] [instance: 09eff2ce-356f-430f-ab30-5de58f58d698] Processing event network-vif-plugged-8a472e87-4a7a-4ad4-9fbb-fd9785136611 _process_instance_event /var/lib/kolla/venv/lib/python3.9/site-packages/nova/compute/manager.py:10205
Further triagging and log analysis should be done by Nova folks to understand why Nova compute didn't boot this VM. I fail to understand some parts.
Regards.